Extract

INTRODUCTION:
Urgent changes are needed in the construction industry to meet short term mitigation goals for climate change. Traditionally, operational environmental flows have been the primary focus of regulations and current attempts to improve the environmental performance of buildings. However, studies have revealed that embodied environmental flows are often underestimated and rarely considered. Embodied environmental flows are particularly significant in the structural systems of tall buildings due to the substantial influence of wind and earthquake loads on structural material requirements.

METHODS:
This work presents a framework for integrating embodied environmental flow assessment into the structural design of tall buildings using comprehensive hybrid methods for life cycle inventory analysis and advanced structural design and finite element modelling techniques. An advanced software tool was developed to formalise the framework and automate the structural design, modelling, analysis, optimisation and embodied energy and embodied greenhouse gas emissions assessment of more than 1,000 structural systems. Through regression analyses, predictive models were constructed for the embodied energy and embodied greenhouse gas emissions per net floor area of 12 unique combinations of structural typologies and structural materials. These models were integrated into a purpose-made online dashboard, which enables engineers and designers to compare alternative structural materials (i.e., 32/40/50 MPa reinforced concrete and steel), structural typologies (i.e., shear wall, outrigger and belt and braced tube) and geometries (i.e., rectangular floor plan geometries) according to the embodied energy and embodied greenhouse gas emissions per net floor area of structural systems. Two case studies were used to illustrate the potential of the framework and software tool in reducing the embodied environmental flows of structural systems for tall buildings of varying heights.

RESULTS:
Results show that all considered building parameters are significant and cannot be neglected in assessing alternative structural systems for tall buildings based on their embodied environmental flows. Increasing the height, slenderness and asymmetry of tall buildings was shown to yield higher embodied environmental flows per net floor area. Decreasing the number of column spans, thereby creating wide-open floor plan spaces, was also shown to yield higher embodied environmental flows per net floor area.

CONCLUSIONS:
The developed framework and software tool have been shown to provide the most precise and sophisticated integration of embodied environmental assessment into the parametric structural design of tall buildings as of yet. Through a simple and user-friendly interface, they enable tall building designers to utilise environmental assessment as a design-assisting tool, rather than as an appraisal method to evaluate a completed building. This will potentially lead to reductions in the environmental effects associated with the construction of tall buildings. Furthermore, by enhancing the consistency, transparency and comprehensiveness of the embodied environmental flow assessment of structural systems, this research has the potential to complement multiscale and holistic approaches that aim to identify solutions that reduce the overall life cycle environmental effects associated with buildings, neighbourhoods and cities.

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